1. Technical Field
Aspects of the present invention relate to a manufacturing method for a semiconductor device using a plurality of semiconductor substrates.
2. Description of the Related Art
Forming semiconductor devices by laminating semiconductor wafers has been studied for the purposes of reducing footprints and the like. For such semiconductor devices, there is a demand to provide electrical continuity between semiconductor wafers. A technique of bonding semiconductor wafers and then electrically connecting circuits provided on the semiconductor wafers is disclosed in US2011/0102657. Specifically, a connection hole is formed in each semiconductor wafer and the connection holes are filled with a conductive material to provide the electrical continuity.
FIG. 8 is a diagram of exemplified defects that can be caused in a semiconductor device when the manufacturing method described in US2011/0102657 is used. With reference to FIG. 8, a first semiconductor substrate 10 and a second semiconductor substrate 20 have been bonded and laminated with a first wiring structure 31 and a second wiring structure 32 interposed therebetween. The first wiring structure 31 includes a first conductive line 311, and the second wiring structure 32 includes a second conductive line 322. In order to connect the first conductive line 311 and the second conductive line 322 electrically, this laminate has been perforated to form holes 65 and 66 which are then filled with a conductive material 68.
As illustrated in FIG. 8, one hole is provided for each conductive line, namely the hole 65 extending toward the second conductive line 322 and the hole 66 extending toward the first conductive line 311. Hence, a foreign substance 531, as illustrated in FIG. 8, would prevent a connection hole from being formed to reach the second conductive line 322, posing a risk of connection failure between the substrates due to defective perforation. Furthermore, even if a hole is formed successfully to reach the first conductive line 311, a foreign substance 532 may prevent a conductive material from being filled in the hole successfully to reach the first conductive line 311, posing a risk of the connection failure between the substrates due to defective filling of the conductive material. As a matter of course, the defective filling may occur in the hole 65, and the defective perforation may happen to the hole 66. As described above, the related art suffers from a low degree of reliability of the electrical continuity between the first conductive line 311 and the second conductive line 322.